Rem #4 22 rimfire rolling block case rupture?

[clearwater]

Twice in many shots, a case has ruptured at the base, including bulging all the way around just above the rim. I noticed the front breech block was not smoothly operating. I oiled it and it works much better now. Perhaps the breech block was not closing completely, thus giving too much headspace?

Was this the source of the problem or is there some other issue I should be looking at.

It is the later takedown model with a thumb screw rather than a lever and I only use standard velocity ammo. It is a shooter, would like to keep using it.

[Hick]

I'm wondering if the barrel is loose allowing it to move out of the proper position-- maybe a little forward due to the takedown screw being a little loose. On my Model 4 the hammer cannot fall unless the breech block is fully closed. Assuming the breech block is closed enough for the hammer to fall, the barrel would have to be a little loose in order to increase the headspace and let the case bulge. If you open the breech block, the face of the barrel should be flush with the inside face of the receiver where the breech block closes.

[OlDeuce]

Could the chamber be a bit over size ???? Ol Deuce

[lucifers]

It's a VERY old gun. Probably has excess headspace. Gunsmith can check that with a 22RF NO-GO gauge.

Can easily be fixed.

If I owned it, I would only shoot it with subsonics for safety.

[John Taylor]

I get them in often with the same problem. Most of the time it is a worn takedown screw or barrel. The later takedown has the screw from the left and seems to have a little more room for tightening. This one can sometimes be fixed by filing a bit off the barrel to let the screw go in a little more ( file toward the muzzle and use layout die to check fit often). The older takedown has the lever on the right and is a little more prone to problems and may be harder to repair. Looks like http://www.rollingblockparts.com/no-4.html
has new takedown screws and levers which might be all that is needed. Other time it may take a little weld on the bottom of the barrel.
To take the lever out you will need to drive out a little pin that is about 1/8" in diameter. It is easy to remove after the barrel is out. The lever has a left hand thread and will screw out easy.

[NoZombies]

John, I think you dropped the wrong link...

[marlinman93]

If the block wasn't completely closed, the hammer wouldn't drop. There's a small amount of clearance, so even a little bit open on the block, and it stops the hammer from dropping.
Sounds like the barrel, takedown pin/lever, etc. to me.

[John Taylor]

John, I think you dropped the wrong link...

Thanks, I fixed it.

[clearwater]

Thanks for all the suggestions. I found one of the side screws holding the hammer to be quite loose. I had just looked at the breach block screw before since that was the part with the obvious grittiness.